Antimicrophonic phototube circuit



March 12, 1940. F. H. GULLIKSEN ANTIMICROPHONIC PHOTOTUBE CIRCUIT Filed May 5, 1959 Unit P Amplifier v INVENTOR Finn H. Gullilcsen.

' A ORNEY WITNESSES: m M

Patented Mar. 12, 1940 PATENT OFFICE ANTIMICROPHONIC PHOTOTUBE CIRCUIT Finn H. Gulllksen, Pittsburgh, Pa., assignor to Westinghouse Electric dz Manufacturing Company, East Pittsburgh, Pa., a corporation-of Pennsylvania Application May 5, 1939, Serial No. 271,952

Claims. (Cl. 250-415) My invention relates to photosensitive apparatus and has particular relation to classifying apparatus used in connection with the manufacture of sheet metal in the steel industry.

The present invention is an outgrowth of experimental work which I have-carried out in providing an arrangement for detecting small holes in sheet steel or the like. The photosensitive apparatus which is used in this work must be highly sensitive, as the holes to be detectedare of small dimensions, and the sheet moves at a high speed which may be of the order of 800 feet per minute or more. Moreover, the photoelectric equipment must necessarily be installed very close to the sheet as it leaves a rolling mill, and, therefore, it is subjected to the mechanical vibrations engendered by steel mill operations.

In working with apparatus for detecting holes in sheet metal provided in accordance with the go teachings of the prior art of which I am aware,

I found that substantial irregular errors in the operation are often present. An analysis of the source of these errors reveals that they arise principally from the mechanical and sonic vibrations in the region of the rolling mill. Ap-

parently the mechanical vibrations and the sounds cause the photosensitive tubes used in the apparatus and their component elements to vibrate. The vibration of the electrodes of the photosensitive tubes, which are mounted in a relatively small metallic container, produces variations in the capacity to ground of the electrodes. A substantial number of photocells are customarily used to cover the total area of the sheet to be scanned. The capacity to ground is,

therefore, considerablebecause the cathode area is large and the variations introduced in the ca-. pacity by the vibrations are appreciable. To further aggravate this situation, the spurious variationsare impressed on the multi-stage amplifier, which of necessity must be used to attain the desired sensitivity, and asa result large irregular errors areproduced.

It is, accordingly, an object of my invention to provide a photosensitive arrangement of high sensitivity that shall operate with consistency for use in a region in which there are substantial ment of high sensitivity for detecting small holes in rapidly moving sheet metal.

In the practice of my invention, radiant en ergy of substantial intensity is projected through any holes existing in the sheet metal and impinges on one or more of a plurality of photoelectric cells connected in parallel. The number of such cells depends in general on the width of the sheet; In a particular installation, my invention was used to detect holes in sheet metal 36 inches wide, and for this purpose nine photoelectric cells of the usual structure were connected in parallel. The anodes vof the photoelectric cells. are coupled through a capacitor to the control electrode'of the first valve of the multistage amplifier that is used in the practice of my invention to attain the desired sensitivity. The cathodes of the photoelectric cells are connected to ground by a wire which is itself enclosed-in a tubular conductor also at ground potential.- The photoelectric cells are disposed in a container to which the conductor is secured and which is-thus also maintained at ground potential. The amplifier is enclosed in a grounded container, and the cathode of the first and other valves in the various stages of ampl fication are connected to the container.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawing, in which the single figure is a diagrammatic view showing a preferred embodiment of my invention.

The apparatus shown in the drawing comprises a pair of sources of radiant energy I, which may be ordinary incandescent lamps. and which project radiations on the surface of the sheet metal 3 that is under observation. The metal is projected in a direction perpendicular to the drawing. It may be moving out of a rolling mill to a storage reel, or it may be moving from a storage reel to a take-up reel. In any case, the sheet moves at a high speed, and there is considerable mechanical vibration and noise in the vicinity in Y which the observations are being made.

Directly under the sheet 3 a conducting box 5 containing a plurality of parallel connected photoelectric cells 1 is disposed. The cells I are arranged staggered in rows under a slot 9, in the top of the box over which the sheet 3 passes in such manner that as the sheet moves its whole area is scanned by the cells.

Each of the cells I has an anode II and a cathode |3. The anodes of the cells are connected together to a common wire l5 and the cathodes are connected to another wire I1. The wire I! passes through a conducting tube l9 projecting from the base of the box 5 and is conductively secured to a water pipe 2|, or a similar conductor, which serves for grounding purposes. The tube 9 is also grounded to the pipe 2| by a wire 22. Another wire 23 extends from the wire I] and is connected to the right wall of the box 5. The tube 9 through which the grounding wire I! extends is provided with a flange 25 at its upper end which engages the box 5. The flange is held in intimate engagement with the inner surface of the box by a nut 21, which is tightly screwed on the tube l9.

The output of the photoelectric cells 1 is impressed on a multi-stage amplifier 29 disposed within another metallic box 3|. Only one stage 33 of the amplifier is shown in detail. The others are all of the usual structure coupled to each other and the first stage in the customary manner.

The first amplifier stage comprises a valve 35, preferably of the high vacuum type, having an anode 31, a cathode 39 and a. control electrode 4 I. A network consisting of a resistor 43 and a capacitor 45 in parallel connect the cathode 39 to an output wire 41. The return wire 41 is connected directly to the left wall of the container 3| and to the control electrode 4| through another rcsistor 49. The resistor and capacitor network provide the usual self-bias for the valve 35.

A metallic conductor 5| provided with flanges 53 at its ends interconnects the boxes 5 and 3|. Each of the flanges 53 is brought into intimate engagement with its adjacent wall by an associated nut 55 which is screwed on the conductor. The wire I5 to which the anodes I of the photoelectric cells 1 are connected extends through an insulating tube 51 disposed within the conductor 5| between the two boxes. When the amplifier box 3| is connected to the junction point of a coupling capacitor 59 and a resistor 6| which is in turn connected to the positive anode supply conductor 63, the coupling capacitor 59 is at its other terminal connected to the control electrode 4|. The anode 31 of the valve 35 is connected through a resistor 65 to the output conductor 6|. A wire 61 passing through the tube 35 through which the boxes 5 and 3| communicate, connects the output conductor 3| on the cathode side to the grounded wire IT. The boxes 5 and 3| are thus completely grounded.

The output of the multi-stage amplifier 29 supplies a solenoid 69 whereby a marking device H is actuated. When 'the sheet metal is perforated, radiant energy penetrates to one or the other of the photo-electric cells I, and current is supplied from the amplifier 29 to the solenoid The marking device H is then actuated and indicates the presence of the hole. Because of the complete grounding of the containers 5 and 3| and the cathodes l3 erratic operation by reason of vibration of the cells 1 or their electrodes H and I3 is prevented.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possiblO. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. For use in an establishment, such as a steel mill, in which mechanical and sonic vibrations of substantial amplitude are present, the combination comprising a plurality of photosensitive devices each having an anode and a cathode, amplifying means for said devices including an electric discharge valve having a control electrode, the factor of amplification of said means being such that substantial errors would be produced in the output thereof by reason of the effect of the mechanical and sonic vibrations on said photosensitive devices, meansincluding a capacitor for coupling said anodes to said control electrode, and means for connecting said cathodes to ground.

2. For use in an establishment, such as a steel mill, in which mechanical and sonic vibrations of substantial amplitude are present, the combination comprising a plurality of photosensitive devices each having an anode and a cathode, amplifying means for said devices including an electric discharge valve having a control electrode, the factor of amplification of said means being such that substantial errors would be present in the output thereof by reason of the effect of the mechanical and sonic vibrations on said photosensitive devices, means including a capacitor for coupling said anodes to said control electrode, and means for connecting said cathodes to ground, said connecting means including a wire which is connected directly to ground and a conducting shield enclosing said wire which is also connected to ground.

3. For use in an establishment, such as a steel mill, in which mechanical or sonic vibrations of substantial amplitude are present, the combination comprising a plurality of photosensitive devices each having an anode and a cathode, multi-stage amplifying means for said devices including an electric discharge valve having a control electrode, the factor of amplification of said means being such that substantial errors would be present in the output thereof by reason of the effect of the sonic vibrations on said photosensitive devices, means including a capacitor for coupling said anodes to said control electrode, and means for connecting said cathodes to ground, said connecting means including a wire which is connected directly to ground and a conducting shield enclosing said wire which is also connected to ground.

4. For use'in an establishment, such as a steel inill, in which sonic vibrations of substantial amplitude are present, the combination comprising a plurality of photosensitive devices each having an anode and a cathode, multi-stage amplifying means for said devices including an electric discharge valve having a control electrode and a principal electrode, the factor of amplification of said means being such that substantial errors would be present in the output thereof by reason of the effect of the sonic vibrations on said photosensitive devices, means including a capacitor for coupling said anodes to said control electrode, means for connecting said principal electrode to ground, and means for connecting said cathodes to ground, said connecting means including a wire which is connected directly to ground and a conducting shield enclosing said wire which is also connected to ground.

5. For use in an establishment, such as a steel amasoo mill, in which sonic vibrations of substantial amplitude are present, the combination comprising a plurality of photosensitive devices each having an anode and a cathode disposed within a conducting container, multi-stage amplifying means for said devices disposed within another conducting container and including an electric discharge valve having a'control electrode and a principal electrode, the factor of amplification of said means being such that substantial errors would be present in the output thereof by reason of the effect of the sonic vibrations on said photosensitive devices, means including a capacitor in said other container and a wire passing between said containers for coupling said anodes to said control electrode, said wire passing through a conducting tube interconnecting said containers and being insulated therefrom, means for connecting said principal electrode to' the wall of said other container, means for connecting said cathodes to said first-mentioned. container, and means for connecting said cathodes to ground, said connecting means including another wire which is connected directly to ground and a conducting shield enclosing said wire which is conductively secured to said firstmentloned container.

FINN H. GULLIKSEN. 

